Halo Nuclei

Assist. Prof. Waleed Subhi Hwash-Department of Physics

eps.waleeds.hwash@uoanbar.edu.iq

The author's official website

In nuclear physics, a nucleus is known as a halo nucleus or is supposed to have a nuclear halo when it has a core nucleus surrounded by a "halo" of orbiting neutrons or protons, which makes the radius of the nucleus noticeably bigger than that expected by the model of liquid drop. The unusual structures have been detected in nuclei close to the drip-lines in place of one of the good applications of  the beams radioactive nuclear. The neutron halo is one of the best exciting discoveries. The first experimental one of a neutron halo is the 11Li, and the 11Li is still the furthermost exciting. The 6He, 11Be, 14Be, 17B are reflected other nuclei which have neutron halos. Also there are a number of nuclides candidates as neutron halo. The new studies have been released to investigate the loosely bound nuclear structure of nuclei, which was not simply existing before. Asymmetric nucleus, shells for high-isospin nuclei, nuclear interactions in a low-density, the lightly bound three-body interactions and the collective motions of a low density nuclear matter are among the current subjects of interesting study of these nuclei. Also the several data propose the existence of a proton halo, in addition to the neutron halo. However, it is not yet fully established.  First, we must define the halo nuclei. In nuclear physics, an atomic nucleus, the radius of the nucleus  is predicted by the liquid drop model through using the formula (), but there are some nucleus’s radius is appreciably larger than that predicted by this formula, these nucleus called a halo nucleus as seen in the following figure:

  The two most studied cases are the two-neutron halo nucleus 11Li and the one-neutron halo nucleus 11Be.

Almost, the halo nucleus may be discovered in experiments of scatterin which show the nucleus to be much bigger than the otherwise predictable value. Typically, the cross section of the nucleus is relative to the cube root of its mass. (This is the same relation as would be seen with a solid sphere.) the 11 Li is One example of a halo nucleus, which has a half life of 8.6 ms. 11Li decays into 11Be with emission of an antineutrino and an electron.

The cross-section of 11Li about 3.16 fm, which is close to that of 32S, or even more impressively that of 208Pb, both much heavier nuclei. It consists of a core of 3 protons and 6 neutrons, and a halo of two independent and weakly bound neutrons. Nuclei which have a neutron halo include 11Be and 19C. A two-neutron halo is 6He, 11Li,14Be, 17B, 19B and 22C. Two-neutron halo nuclei are called Borromean because of it break into three fragments. 8He and 14Be both show a four-neutron halo. The following table is list of known isotopes with nuclear halo.